Much Uncertainty Remains Around Late-Week Blizzard Potential

With only a few days to go before snow could start breaking out across the eastern seaboard, there is still a lot to figure out with our impending storm. Many of the same questions that our forecasters were trying to answer yesterday remain on the foggy side today, as guidance continues to waffle back and forth between a crippling I-95 blizzard and a close-miss.

With that said, seeing as the storm begins later on Wednesday, our team is going to take our first shot at what may unfold later this week.

First off, regardless of what this system ends up doing, it will be extremely powerful. As far as winter storms go, any low pressure system that dips below 970 mb is fairly rare in nature, and if guidance can agree on anything at this point, it’s that we could be dealing with a sub 965 mb storm by time it reaches the northern Atlantic Ocean. That will mean strong winds extending out hundreds of miles, large waves along the coastline, and heavy precipitation reaching far-out in all directions.

In situations like these where energy sampling is still struggling and we’re seeing convective feedback issues among global guidance, it’s best to go with mesoscale guidance and ensembles. Even then though, we’re still seeing a far amount of disagreement, with reliable models such as the RGEM and higher resolution NAM showing a major snowstorm along I-95, and the 12km NAM showing a storm well offshore. The bigger issue here is how slight the differences are aloft at 500 mb (upper-level pattern). Slight shifts in the overarching pattern are delaying or speeding up the energy phasing that creates our major storm, and thus leading to these larger-scale differences down at the surface. But what we’re trying to get at here, is that very minute changes in what happens at 500 mb could easily shift the heaviest snowfall 50-100 miles east or west.

With all of that said, this is what our first take on the potential late-week blizzard looks like:

The storm originates well to the south near the Bahamas, which is quite unusual to begin with, and then starts deepening and expanding off the southeast coastline. With such frigid temperatures nationwide, one of the things our team is concerned about (and has been looked over a good bit across the media so far), is the winter potential as far south as Florida. As our storm gathers, its likely enough cold air will be in place to change rain over to a wintry mix and possibly even a period of snow from the Florida-Georgia borderline to coastal South Carolina. Some guidance even suggests some light to moderate accumulation will be possible. Again, that will all be dependent on where the storm forms and moves next.

From here, the storm should continue in a north-northeasterly direction, quickly strengthening and expanding. Pressure will drop below 1000 mb’s, winds will pick-up and spread out, and rough waters will impact the entire eastern coastline. Wednesday morning through the afternoon and evening could feature rain and wintry precipitation spreading from Savannah GA through Charleston SC and into eastern North Carolina.

The map above depicts the chances of locations from Florida to New England receiving plowable snowfall (this is due to how much uncertainty there still is at this point). If things take a middle route like we show here, there will be a low chance of plowable snowfall (4+ inches) from Raleigh NC to Washington DC to Albany NY and up into Burlington VT. Just east of there along and SE of I-95, we think there’s a moderate chance (50%) of plowable snowfall, which include the extreme southern DELMARVA up through eastern suburbs of New York City, southern New England, and a good portion of northern New England. The only areas where we’re really confident in plowable snowfall, is eastern Maine. At this point, a large deformation band should form and expand far enough out to the west to almost guarantee at least 4 inches of snowfall.. Possibly much higher.

Now while the map above reflects our current thoughts, we can’t rule out either of the other two scenarios. A crippling east coast blizzard or a near-miss with little impact.

Here’s the first “low-end” scenario, which we give a 25% chance of verifying. In this situation, the phasing occurs earlier, and our low tracks much closer to the coast. This would bring heavy snowfall from Philadelphia to Boston and on into New England, while areas further west and parts of the southeast still see light to moderate snowfall.

This type of solution reminds us much of “The Boxing Day Blizzard,” where a very similar situation unfolded. A lack of accurate sampling led to a “last-minute” shift west of the storm, bringing heavy snow and blizzard conditions up and down the I-95 corridor. With that said, we are not by any means forecasting that at this point, but cannot totally rule it out either.
The second solution, which we give a slightly higher chance at 30% of happening, shows the upper-level energy phasing together much later (or not completely), and allows our storm to stay much further offshore. In this type of scenario, the southeast sees a sizable snowstorm, which the middle and northern half of the eastern seaboard gets whiffed by some light to moderate snowfall. Again, even in this scenario its likely that eastern Maine gets a pretty good hit.
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What’s important to takeaway at this point, just 2-3 days out, is that a major storm will develop over the next 48 hours, and begin moving north-northeast through the end of the week. The storm will have dangerous winds, heavy precipitation, and be capable of producing powerful waves, but it’s exact track is not set in stone, and small differences could have very large implications at the surface. For now, we expect a track somewhere in the middle, with light and moderate snowfall up and down most of I-95, while heavy snowfall remains mostly offshore. We caution assuming this is a final scenario however, as a track that brings much more significant impacts or no impacts at all is still very much on the table. As always, stay tuned to our latest forecasts, and expect another update tomorrow morning.

Currently leads business development and forecasting across all sectors and is the Founder and CEO. Pecoriello founded WeatherOptics in 2010 as a blog called, Wild About Weather, which quickly gained a following. He also launched an app in 2013 called, Know Snow, designed to accurately forecast the chances of school closings.